The invention relates to an apparatus for the energy-optimized hydraulic control of at least one double-action working cylinder of a work machine.
In work machines, working cylinders serve the actuation of any accessory equipment or for the luffing movement of boom systems. The stroke movement as a rule takes place against the load; the retraction of the piston rod, in contrast, is effected unpressurized by the load. In known interconnections of working cylinders in mobile work machines, the retraction of the piston rod is implemented with a pushing load by a restriction control to brake the inward movement speed. On the restriction, the potential energy of the pressurized volume flow displaced by the load on the cylinder is converted into heat. The potential energy present is not only destroyed; cooling power must rather additionally be applied for the heat dissipation within the machine.
A common embodiment of the hydraulic working cylinder in mobile cylinders is the differential cylinder. If the latter is retracted by means of a restriction control and a pressing load, it must be ensured that a refilling of the rod-side cylinder chamber is guaranteed. This is possible, on the one hand, by the switching on of a corresponding supply volume flow through the work pumps; on the other hand, a corresponding refilling of the rod-side cylinder chambers can be carried out by a return of the restricted volume flow. Due to the return of the restricted volume flow, a division thereof is made corresponding to the area ratio of the hydraulic cylinders. In this respect, one portion flows into the rod-side chambers of the cylinders; the other portion is led into the tank.
It is desirable on the storage of the potential energy to acquire as much displaced oil volume as possible with a pressure which is as high as possible. Based on the common interconnection with a return of a partial quantity into the rod-side chambers of the hydraulic cylinders, only a partial quantity of the displaced oil volume is available for storage. The returned partial quantity is additionally restricted, based on the restriction control, from a high pressure level to a low pressure level. Three disadvantages therefore result: The quantity of oil is split; some of the energy is destroyed by the restriction control; and the heat loss additionally has to be led off from the cooling system of the machine.